Centrifugal fan and fan frame thereof

ABSTRACT

A centrifugal fan, comprising a frame and a first guide portion. The frame comprises a bottom portion and a curved wall connected thereto. The curved wall comprises an airflow inlet. The first guide portion disposed along the curved wall at the bottom portion comprises a beginning area, a middle area, and an ending area. The middle area connects the beginning and the ending areas, and the beginning area extends from the airflow inlet. The beginning area has a width less than that of the ending area, and the beginning area has a height greater than that of the ending area.

BACKGROUND OF THE INVENTION

The invention relates to a centrifugal fan and, in particular, to acentrifugal fan with a fan frame that can enhance fan performancesubstantially. Electronic devices generally produce heat duringoperation, and thus the demand for effective heat-dissipation deviceshas increased. Therefore, a heat-dissipating device or a centrifugal fanmust offer optimal performance to dissipate the excess heat. As shown inFIG. 1A, a conventional centrifugal fan 1 includes a fan frame 10′ andan impeller 20′. FIG. 1A is a perspective view of a combination of thefan frame 10′ and the impeller 20′. FIG. 1B is a perspective view of thefan frame 10′. The fan frame 10′ includes a frame 15′ and a sleeve 14′.The impeller 20′ is disposed in the fan frame 10′ through the sleeve14′. The frame 15′ of the fan frame 10′ comprises a curved wall 11′, abottom portion 12′, and a first guide portion 13′.

Higher air pressure increases the amount of airflow and speed, and viceversa. The fan frame structure 10′ is one of the main factors affectingthe air pressure level. In the conventional design, when the fanoperates, airflow is produced and flows along the curved wall betweenthe guide portion 13′ and the impeller 20′. However, since the guideportion 13′ has a flat elevation, as shown in FIG. 1C, the airflowsurrounding the impeller 20′ is disturbed, thereby producing cyclonicairflow and reducing air pressure. Thus, the total performance of thefan is reduced accordingly. Specifically, turbulent flow is produced atthe inlet, and a certain level of flow resistance is generated. Thus,the guide portion 13′ with a flat elevation is unable to efficientlyguide the airflow, but adversely reduces the heat dissipationperformance of the fan.

Since the above method does not satisfy performance demands, there isstill a need for a fan structure offering enhanced performance withoutincreasing the overall size of the fan that can minimize the airflowdisturbance produced along a flow path between the fan frame and theimpeller to maximize the airflow and air pressure.

SUMMARY

An embodiment of the invention, therefore, provides a centrifugal fanthat eliminates the shortcomings described above and increases heatdissipation performance.

The invention provides a centrifugal fan comprising a frame and a firstguide portion. The frame comprises a bottom portion and a curved wallconnected thereto. The curved wall comprises an airflow inlet. The firstguide portion disposed along the curved wall at the bottom portioncomprises a beginning area, a middle area, and an ending area. Themiddle area connects the beginning and the ending areas, and thebeginning area extends from the airflow inlet. The beginning area has awidth less than that of the ending area, and the beginning area has aheight greater than that of the ending area.

The frame further comprises a top portion. The beginning area has aheight of less than 30% of a distance measured from the bottom portionto the top portion.

At least the beginning area, the middle area, or the ending areacomprises a sloped surface.

One of the beginning area, the middle area, or the ending area comprisesa flat surface parallel to the bottom portion.

In an embodiment of the invention, the bottom portion and the firstguide portion are integrally formed.

The frame further comprises a top portion comprising a second guideportion, disposed corresponding to the first guide portion. A distancebetween the first guide portion and the second guide portion is at least70% of a distance from the bottom portion to the top portion.

The first guide portion and the second guide portion are symmetricallyformed.

Furthermore, the top portion and the second guide portion are integrallyformed.

An embodiment of the invention further provides a centrifugal fancomprising an impeller and a fan frame. The fan frame comprises a topportion, a bottom portion, and a curved wall. The curved wall isconnected to the top portion and the bottom portion, surrounding theimpeller. The curved wall comprises an airflow inlet. The top portionand the bottom portion each comprises at least one guide portion,disposed along the curved wall such that a flow path is formed withinthe guide portion, the curved wall, and the impeller. Additionally, thewidth of the flow path increases radially from the airflow inlet alongthe impeller, and the height of the flow path increases axially from theairflow inlet along an axis of the impeller.

The height of the flow path at the airflow inlet is at least 70% of adistance between the top portion and the bottom portion.

DESCRIPTION OF THE DRAWINGS

Embodiments of the invention can be more fully understood by reading thesubsequent detailed description in conjunction with the examples andreferences made to the accompanying drawings, wherein:

FIG. 1A is a schematic diagram of a conventional centrifugal fan;

FIG. 1B is a schematic perspective diagram of a fan frame of theconventional centrifugal fan;

FIG. 1C is a side view of the frame of FIG. 1B;

FIG. 2A is a schematic view of a centrifugal fan of a first embodimentof the invention;

FIG. 2B is a schematic view of a centrifugal fan frame of a firstembodiment of the invention;

FIG. 2C is a local enlarged view of the centrifugal fan frame of FIG.2B;

FIG. 2D is a side view of the centrifugal fan frame according to thefirst embodiment of the invention;

FIG. 2E is a top view of the centrifugal fan frame according to thefirst embodiment of the invention;

FIG. 3 is a side view of the centrifugal fan frame according to a secondembodiment of the invention;

FIG. 4 shows a relationship between air pressure and flow volume of acentrifugal fan frame according to the second embodiment of theinvention; and

FIG. 5 is a side view of the centrifugal fan frame according to avariation of the invention.

DETAILED DESCRIPTION First Embodiment

Please refer to FIG. 2A. FIG. 2A is a schematic view of a centrifugalfan 2 of a first embodiment of the invention. The centrifugal fan 2comprises a fan frame 10 and an impeller 20.

Please refer to FIG. 2B. FIG. 2B is a schematic view of the fan frame10. The fan frame 10 comprises an outer frame 15, a curved wall 11, abottom portion 12, a first guide portion 13, and a sleeve 14. Theimpeller 20 is disposed within the outer frame 15 through the sleeve 14.The curved wall 11 encircling the impeller 20 is connected to the bottomportion 12.

Please refer to FIG. 2C. FIG. 2C is a local enlarged view of thecentrifugal fan frame 10 of FIG. 2B. The first guide portion 13encircling the sleeve 14 is also disposed on the bottom portion 12. Thebottom portion 12 and the first guide portion 13 are integrally formed.

A flow path P is formed within the first guide portion 13, the curvedwall 11, and the impeller 20. Air flows in the flow path P according toarrows shown in FIGS. 2D and 2E. The flow path P increases its width andheight along the airflow direction such that the air can flow smoothly,increasing total performance of the fan. In this embodiment, thevariation in the size of the flow path P is achieved by varying thestructure of the first guide portion 13. Details of the variation willbe described in the following.

The first guide portion 13 can be divided into a beginning area 131, amiddle area 132, and an ending area 133. The beginning area 131 islocated at an airflow inlet of the fan frame 10. The middle area 132connects the beginning area 131 and the ending area 133. The beginningarea 131, the middle area 132, and the ending area 133 each has a slopedsurface or a flat surface such that the height of the first guideportion 13 decreases from the beginning area 131, the middle area 132,and the ending area 133, respectively.

Since the beginning area 131, the middle area 132, and the ending area133 each has a different sloped angle, and each has a different height,H₁, H₂, and H₃, respectively. In this embodiment, the beginning area 131has the largest height H₁, and the ending area 133 has the smallestheight H₃.

The distance L between the top portion 16 and the bottom portion 12 ofthe fan frame 10 is defined as the maximum height of flow path P, andthe height H₁ is about 20-30% of the maximum height L of flow path P.According to the flow path, the depth of flow path P at the airflowinlet is about 70% of the distance between the top portion 16 and thebottom portion 12 of the fan frame 10. As shown in FIG. 2E, the width ofthe flow path P is narrower at the beginning area 131 and wider at theending area 133.

In detail, when the width of the flow path P at the beginning area 131is referred to as w₁, the width of the flow path P at the middle area132 is referred to as w₂, and the width of the flow path P at the endingarea 133 is referred to as w₃, w₁ is the maximum width, and the w₃ isthe minimum width. The width of the flow path P gradually increases fromairflow inlet such that air pressure and airflow volume are augmentedfor smooth airflow. Thus, the fan according to the above embodimentproduces less turbulence, increasing overall performance.

Second Embodiment

Please refer to FIG. 3. FIG. 3 is a side view of the centrifugal fanframe 10 according to a second embodiment of the invention. The elementscommon to the first embodiment are omitted. As shown in FIG. 3, the topportion 16 further comprises a second guide portion 17, disposedcorresponding to the first guide portion 13. The distance D between thefirst guide portion 13 and the second guide portion 17 near the airflowinlet is at least 70% of the distance L between the top portion 16 andthe bottom portion 12. Since the second guide portion 17 and the firstguide portion 13 are formed symmetrical to a plane parallel to thehorizon, the shapes of the second guide portion 17 and the first guideportion 13 are substantially identical.

The depth of flow path P varies from D₁, D₂, and D₃ from the right-mostside in FIG. 3 toward −x direction. Thus, D₁ is less than D₂, and D₃. D₃is substantially equal to the distance L between the top portion 16 andthe bottom portion 12. As mentioned, the width of the flow path P or thefirst guide portion 13 is gradually increased from the beginning area131 toward a radial direction of the impeller 20, as indicated by widthsw₁, w₂, and w₃. Thus, the width and height of the flow path P are bothgradually increased, providing better performance and smoother flow andreducing turbulence.

Furthermore, FIG. 4 shows a relationship between air pressure andairflow volume of a centrifugal fan frame according to the secondembodiment of the invention. The data on the curve are obtained byexperiments. Curve A represents the results of the second embodiment ofthe invention. Curve B represents the results of the conventionalcentrifugal fan. For example, in the same air pressure condition of 10mmH₂O, the amount of airflow produced by the conventional centrifugalfan is found to be 0.4 m³/mm, and the airflow volume of the secondembodiment is 0.45 m³/mm, which is higher than that of the conventionalfan. In addition, if provided with the same amount of airflow, thepressure in the fan frame according to the curve A is higher than thepressure of the conventional fan as shown by curve B. Thus, it is provedby FIG. 4 that the flow path with increasing size can eliminate theshortcomings of the conventional fan, increasing air pressure and amountof air airflow and minimizing turbulent flow. Hence, overall fanperformance can be improved accordingly.

In other variations of the above embodiments, the beginning area, middlearea, and ending area of the first or the second guide portion 13 or 17can be either flat or sloped. When an area has a flat surface, the areais parallel to the bottom portion 12 or the top portion 16 of the frame15. Thus, each guide portion 13 or 17 has a combination of flat andsloped surface.

FIG. 5 shows one of the possible combinations. In this variation, thebeginning area 131 of the bottom portion 12 has a flat surface. Themiddle area 132 and the ending area 133 are sloped. Note that no matterwhich area is flat or sloped, the height H₁ of the beginning area 131must be greater than the height H₃ of the ending area 133. Thus, thevariation provides the same effect as the above embodiments.

Hence, the performance of the centrifugal fan is optimized and theamount of the airflow and air pressure of the fan is also maximized.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. On the contrary, it isintended to cover various modifications and similar arrangements aswould be apparent to those skilled in the art. Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A centrifugal fan frame, comprising: a frame having a bottom portionand a curved wall connected thereto; and a first guide portion, disposedalong the curved wall at the bottom portion, comprising a beginningarea, a middle area, and an ending area; wherein the middle areaconnects the beginning and the ending areas, the beginning area has awidth less than that of the ending area, and the beginning area has aheight greater than that of the ending area.
 2. The centrifugal fanframe as claimed in claim 1, wherein the frame further comprises a topportion, the beginning area has a height less than 30% of a distancemeasured from the bottom portion to the top portion.
 3. The centrifugalfan frame as claimed in claim 1, wherein the curved wall furthercomprises an airflow inlet.
 4. The centrifugal fan frame as claimed inclaim 3, wherein the beginning area extends from the airflow inlet. 5.The centrifugal fan frame as claimed in claim 1, wherein the beginningarea, the middle area, or the ending area comprises a sloped surface,respectively.
 6. The centrifugal fan frame as claimed in claim 1,wherein the beginning area, the middle area, or the ending areacomprises a flat surface parallel to the bottom portion.
 7. Thecentrifugal fan frame as claimed in claim 1, wherein the bottom portionand the first guide portion are integrally formed.
 8. The centrifugalfan frame as claimed in claim 1, wherein the frame further comprises atop portion having a second guide portion disposed corresponding to thefirst guide portion.
 9. The centrifugal fan frame as claimed in claim 8,wherein a distance between the first guide portion and the second guideportion is at least 70% of a distance from the bottom portion to the topportion.
 10. The centrifugal fan frame as claimed in claim 8, whereinthe first guide portion and the second guide portion are symmetricallyformed with respect to a plane.
 11. The centrifugal fan frame as claimedin claim 8, wherein the top portion and the second guide portion areintegrally formed.
 12. A centrifugal fan, comprising: an impeller; and afan frame, comprising: a top portion; a bottom portion; and a curvedwall, connected with the top portion and the bottom portion, andsurrounding the impeller; wherein the top portion or the bottom portioncomprises at least one guide portion, disposed along the curved wallsuch that a flow path is formed within the guide portion, the curvedwall, and the impeller.
 13. The centrifugal fan as claimed in claim 12,the curved wall further comprises an airflow inlet.
 14. The centrifugalfan as claimed in claim 13, wherein the flow path has a width increasingradially from the airflow inlet along the impeller, and the flow pathhas a height increasing axially from the airflow inlet along an axis ofthe impeller.
 15. The centrifugal fan as claimed in claim 13, whereinthe height of the flow path at the airflow inlet is at least 70% of adistance between the top portion and the bottom portion.
 16. Acentrifugal fan, comprising: an impeller; and a frame receiving theimpeller therein, and having at least one guide portion formed in theframe; wherein the guide portion has a gradually changed height forsmoothing an airflow passing through the heat dissipation device. 17.The centrifugal fan as claimed in claim 16, the curved wall furthercomprises an airflow inlet.
 18. The centrifugal fan as claimed in claim16, wherein the flow path has a width increasing radially from theairflow inlet along the impeller, and the flow path has a heightincreasing axially from the airflow inlet along an axis of the impeller.19. The centrifugal fan as claimed in claim 16, wherein the height ofthe flow path at the airflow inlet is at least 70% of a distance betweenthe top portion and the bottom portion.